In radio and telecommunication applications a dipole antenna is the simplest and most widely used class of antenna. The dipole is any one of a class of antennas producing a radiation pattern approximating that of an elementary electric dipole with a radiating structure supporting a line current so energized that the current has only one node at each end. A dipole antenna commonly consists of two identical conductive elements such as metal wires or rods, which are usually bilaterally symmetrical. The driving current from the transmitter is applied, or for receiving antennas the output signal to the receiver is taken, between the two halves of the antenna. Each side of the feedline to the transmitter or receiver is connected to one of the conductors. This contrasts with a monopole antenna, which consists of a single rod or conductor with one side of the feedline connected to it, and the other side connected to some type of ground. A common example of a dipole is the “rabbit ears” television antenna found on broadcast television sets.
Automobiles are fitted with antennas for various uses, as for example, for receiving radio signals, Wi-Fi and GPS signals, mobile communication signals, etc. Automobile to automobile communication (C2C) is now becoming a phenomenon to enable automobiles to communicate with each other for various reasons including providing a safe driving experience on public highways.
Automobile to Everything (C2X) communication is believed to be a key technology in contributing to safe and intelligent mobility in the future. Today's vehicles are equipped with many wireless services to receive radio and television broadcasting and to support communication like cellular phone and GPS for navigation. Even more communication systems will be implemented for “intelligent driving”, such as wireless access in vehicular environments (WAVE), a vehicular communication system. As a result, the number of automotive antennas is increasing and the miniaturization requirements are becoming an important factor to reduce the cost. Combining two or more antennas for different frequency spectrums in one antenna structure is therefore an important asset for automotive antenna design.
C2X communication systems in Europe and USA make use of the IEEE802.11p standard, which operates in bands ITS-G5A, ITS-G5B and ITS-G5D: 5.855-5.925 GHz
The Japanese ARIB STD-T109 standard dedicates the 700 MHz band to Intelligent Transport Systems. The operating frequency band to be used shall be 755.5-764.5 MHz, with a center frequency of 760 MHz and an occupied bandwidth of 9 MHz or less.
Since there is a dependency of antenna size on frequency, supporting a frequency as low as 760 MHz poses challenges in terms of keeping the height of the antenna design within the specification of the application.